In a typical cable television system, each subscriber is provided with a set-top unit, also called a set-top box or set-top terminal. The set-top unit is a piece of electronic equipment that is used to connect the subscriber's television, and potentially other electronic equipment, to the cable network. The set-top unit is usually connected to the cable network through a co-axial wall outlet.
The set-top unit is essentially a computer that is programmed to process the signals from the cable network so as to provide the subscriber with the services of the cable system. These services from the cable television company typically include access to a number of television channels and, perhaps, an electronic program guide. Additionally, premium channels may also be provided to subscribers for an additional fee. Other video programming services such as pay-per-view events and video-on-demand may also be provided over the cable network. The set-top box is programmed to provide these and all the other services of the cable system to the subscriber.
However, the services of the cable system are not necessarily limited to providing television programming. Some cable companies now offer internet access and e-mail over their cable networks at speeds much faster than are available over conventional telephone lines. Some cable companies also offer telephone service. It is anticipated in the future that more and more data services will be provided over the cable network. Eventually, each home or office may have a single connection, via the cable network, to all electronic data services.
When a new set-top unit is connected to the cable network, it must be initialized. To initialize a set-top unit, the unit must be provided with the programming required to allow it to function within the specific cable system to which it is connected and to thereby provide the services for which the subscriber has paid. Each cable system, built and managed by different cable system operators, may be set-up and function differently than other cable systems. Consequently, initializing a set-top unit includes physically connecting the set-top unit to the cable system so that the unit receives the signal from the cable system and programming the set-top unit to identify and tune a control channel within the signal from the cable system.
The control channel is a piece of broadband signal used for supervisory services. Specifically, the control channel is used to provide the set-top unit with instructions and data sent by the cable system operator. Without the data from the control channel, the set-top unit will be unable to make appropriate use of the signal from the cable system, e.g., recognize television programming on the in-band channels of the composite signal from the cable system. The headend is the facility from which the cable system operator broadcasts the control channel and television signals and provides other services over the cable system.
The frequency for the control channel could be programmed into the set-top unit during manufacture. However, different cable systems will likely use different frequencies to transmit their control channel. If more than one control channel is used, the configuration of control channels is even more likely to vary from system to system. Consequently, each set-top unit must be able, when connected to the cable system, to dynamically locate the control channel or channels so as to receive the necessary information required to allow the set-top unit to operate with that particular cable system.
Typical set-top units have a control channel tuner which is used to tune the control channel from within the composite signal received over the cable television system. The data of the control channel is the provided by the control channel tuner to the set-top unit's circuitry. Conventionally, in order to locate a control channel when a new set-top unit is first connected to a cable system, the control channel tuner in the set-top unit scans through the entire frequency band that might contain the control channel(s) until the control channel(s) is located. This involves a brute force search which requires stopping and testing each possible frequency.
Consequently, this search for the control channel requires a period of time during which the set-top unit cannot be used to watch television or provide any other services of the cable system to a subscriber. Consequently, there is a need in the art for an improved method and system of locating the control channel of a cable television system so as to minimize the time the set-top unit must spend searching for the control channel during which time other functions of the set-top unit are not available.